Power tool having rotary input control

ABSTRACT

A power tool includes a housing, a motor, an output member driven by the motor, and a reaming attachment coupled to the output member. The reaming attachment has a front end portion selectively driven in rotation by the output member to drive a fastener into a workpiece, and a reaming portion selectively driven in rotation by the output member to remove material from an end surface of a conduit. A rotational motion sensor in the housing is operable to detect rotational motion of the housing about an axis. A controller receives a signal indicative of rotational motion from the sensor, determines a direction of the rotational motion of the housing, and drives the motor in a direction corresponding to the direction of rotational motion of the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/773,696, filed on Feb. 22, 2013, which is acontinuation-in-part of U.S. patent application Ser. No. 13/404,620,filed on Feb. 24, 2012, (now U.S. Pat. No. 8,418,778, issued Apr. 16,2013), which application is a continuation-in-part of U.S. patentapplication Ser. No. 13/120,873 filed on May 13, 2011, (now U.S. Pat.No. 8,286,723, issued Oct. 16, 2012), which is a national phase ofPCT/US2011/020511 filed Jan. 7, 2011. This application also claims thebenefit of U.S. Provisional Application No. 61/746,606, filed on Dec.28, 2012, to U.S. Provisional Application No. 61/292,966, filed on Jan.7, 2010, and to U.S. Provisional Application No. 61/389,866, filed onOct. 5, 2010. The entire disclosures of each of the above applicationsare incorporated herein by reference.

FIELD

The present disclosure relates generally to power tools, such as a powerscrewdriver, and, more particularly, to a control scheme that controlsrotation of an output member of a tool based on rotary user input.

BACKGROUND

In present-day power tools, users may control tool output through theuse of an input switch. This can be in the form of a digital switch inwhich the user turns the tool on with full output by pressing a buttonand turns the tool off by releasing the button. More commonly, it is inthe form of an analog trigger switch in which the power delivered to thetool's motor is a function of trigger travel. In both of theseconfigurations, the user grips the tool and uses one or more fingers toactuate the switch. The user's finger must travel linearly along oneaxis to control a rotational motion about a different axis. This makesit difficult for the user to directly compare trigger travel to outputrotation and to make quick speed adjustments for finer control.

Another issue with this control method is the difficulty in assessingjoint tightness. As a joint becomes tighter, the fastener becomes morereluctant to move farther into the material. Because the tool motorattempts to continue spinning while the output member slows down, areactionary torque can be felt in the user's wrist as the user increasesbias force in an attempt to keep the power tool stationary. In thiscurrent arrangement, the user must first sense tightness with the wristbefore making the appropriate control adjustment with the finger.

This section provides background information related to the presentdisclosure which is not necessarily prior art.

SUMMARY

An improved method is provided for operating a power tool. The methodincludes: monitoring rotational motion of the power tool about an axisusing a rotational motion sensor disposed in the power tool; determininga direction of the rotational motion about the axis; and driving theoutput member in a direction defined by the detected rotational motionof the tool, where the output member is driven by a motor residing inthe power tool. This approach results in a highly intuitive method foroperating the tool similar to the use of a manual screwdriver.

In one aspect of the disclosure, the improved operation methods areincorporated into a power tool. The power tool is comprised of: ahousing; an output member at least partially contained in the housingand configured to rotate about a longitudinal axis; a motor contained inthe housing and drivably connected to the output member to impart rotarymotion thereto; a rotational motion sensor arranged in the housing at alocation spatially separated from the output member and operable todetect rotational motion of the housing about the longitudinal axis ofthe output member; and a controller configured in the housing to receivea signal indicative of rotational motion from the rotational motionsensor. The controller determines a direction of the rotation motion ofthe housing about the axis and drives the motor in the same direction asthe rotational motion of the housing.

In another aspect of the disclosure, the power tool may be furtherconfigured with a reamer tool.

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

FIG. 1 is a perspective view of an exemplary power screwdriver.

FIG. 2 is a longitudinal section view of the power screwdriver of FIG.1.

FIG. 3 is a perspective view of the power screwdriver of FIG. 1 with thehandle being disposed in a pistol-grip position.

FIG. 4 is an exploded perspective view of the power screwdriver of FIG.1.

FIGS. 5A-5C are fragmentary section views depicting different ways ofactuating the trigger assembly of the power screwdriver of FIG. 1.

FIGS. 6A-6C are perspective views of exemplary embodiments of thetrigger assembly.

FIG. 7 is a schematic for an exemplary implementation of the powerscrewdriver.

FIGS. 8A-8C are flow charts for exemplary control schemes for the powerscrewdriver.

FIG. 8D is a flow chart for another embodiment of a control scheme forthe power screwdriver.

FIGS. 9A-9E are charts illustrating different control curves that may beemployed by the power screwdriver.

FIG. 10 is a diagram depicting an exemplary pulsing scheme for providinghaptic feedback to the tool operator.

FIG. 11 is a flow chart depicting an automated method for calibrating agyroscope residing in the power screwdriver.

FIG. 12 is a partial sectional view of the power screwdriver of FIG. 1illustrating the interface between the first and second housingportions.

FIG. 13A-13C are perspective views illustrating an exemplary lock barassembly used in the power screwdriver.

FIG. 14A-14C are partial sectional views illustrating the operation ofthe lock bar assembly during configuration of the screwdriver from the“pistol” arrangement to the “inline” arrangement.

FIG. 15 is a flowchart of an exemplary method for preventing anoscillatory state in the power screwdriver.

FIG. 16 is a fragmentary section view depicting an alternative triggerswitch assembly.

FIGS. 17A-17C are cross-sectional views illustrating alternative on/offand sensing mechanisms.

FIG. 18 is a flowchart for another exemplary control scheme for thetool.

FIGS. 19A-19B are diagrams illustrating an exemplary self-lockingplanetary gear set.

FIG. 20 is a perspective view of a second exemplary power screwd river.

FIG. 21 is a perspective view of a third exemplary power screwdriver.

FIGS. 22A-B are cross-sectional views of the exemplary power screwdriverof FIG. 21, illustrating one way to activate the reaming tool. and

FIGS. 23A-B are cross-sectional views of the exemplary power screwdriverof FIG. 21, illustrating a second way to activate the reaming tool.

FIG. 24 is a perspective view of another exemplary power screwdriver andreaming tool.

FIG. 25A is a side view of the power screwdriver and reaming tool ofFIG. 24.

FIG. 25B is an exploded view of a portion of the power screwdriver andreaming tool of FIG. 24.

FIG. 25C is a partial cross-sectional view of a portion of the powerscrewdriver and reaming tool of FIG. 24.

FIGS. 26A and 26B are side views of the power screwdriver and reamingtool of FIG. 24 in operation.

FIG. 27 is a perspective view of another embodiment of a screwdriver andreaming accessory for a power tool.

FIG. 28A is a perspective view of another embodiment of an exemplarypower tool with improved user input control configured as a powerwrench.

FIG. 28B is a top view of the power tool of FIG. 28A.

FIG. 29 is a schematic diagram of a control circuit for the power toolof FIGS. 28A and 28B.

FIG. 30A depicts a first exemplary control scheme for the power tool ofFIGS. 28A-29.

FIG. 30B depicts a second exemplary control scheme for the power tool ofFIGS. 28A-29.

FIGS. 31A-31C depict an exemplary actuator for selecting the directionof operation for the power tool of FIGS. 28A-29.

FIG. 32A is a perspective view of another embodiment of an exemplarypower tool with improved user input control configured as an alternativeembodiment of a power wrench

FIG. 32B is a top view of the alternative embodiment of the power socketwrench of FIG. 31A.

FIG. 33 is a perspective view of another embodiment of an exemplarypower tool with improved user input control configured as an impactdriver.

FIGS. 34-36 are side views partially in section of the impact driver ofFIG. 33.

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure. Correspondingreference numerals indicate corresponding parts throughout the severalviews of the drawings.

DETAILED DESCRIPTION

With reference to FIGS. 1 and 2, an exemplary power screwdriver isindicated generally by reference number 10. The screwdriver 10 iscomprised generally of an output member 11 configured to rotate about alongitudinal axis 8 and a motor 26 driveably connected to the outputmember 11 to impart rotary motions thereto. Tool operation is controlledby a trigger switch, a rotational rate sensor and a controller in amanner further described below. A chuck or some other type of toolholder may be affixed to the end of the output member 11. Furtherdetails regarding an exemplary bit holder are set forth in U.S. patentapplication Ser. No. 12/394,426 which is incorporated herein byreference. Other components needed to construct the screwdriver 10 arefurther described below. While the following description is providedwith reference to screwdriver 10, it is readily understood that thebroader aspects of the present disclosure are applicable to other typesof power tools, including but not limited to tools having elongatedhousings aligned concentrically with the output member of the tool.

The housing assembly for the screwdriver 10 is preferably furthercomprised of a first housing portion 12 and a second housing portion 14.The first housing portion 12 defines a handle for the tool and can bemounted to the second housing portion 14. The first housing portion 12is rotatable in relation to the second housing portion 14. In a firstarrangement, the first and second housing portions 12, 14 are alignedwith each other along the longitudinal axis of the tool as shown in FIG.1 This arrangement is referred to herein as an “inline” configuration.

The screwdriver 10 may be further configured into a “pistol-type”arrangement as shown in FIG. 3. This second arrangement is achieved bydepressing a rotation release mechanism 130 located in the side of thesecond housing portion 14. Upon depressing the release mechanism 130,the first housing portion 12 will rotate 180 degrees in relation to thesecond housing portion 14, thereby resulting in the “pistol-type”arrangement. In the second arrangement, the first and second housingportions 12, 14 form a concave elongated groove 6 that extends from oneside of the tool continuously around the back to the other side of thetool. By placing an index finger in the groove 6 on opposing sides, thetool operator can better grip the tool, and the positioning of the palmdirectly behind the longitudinal axis 8 allows the operator to bettercontrol the screwdriver.

With reference to FIGS. 2 and 4, the first housing portion 12 can beformed from a pair of housing shells 41, 42 that can cooperate to definean internal cavity 43. The internal cavity 43 is configured to receive arechargeable battery pack 44 comprised of one or more battery cells. Acircuit board 45 for interfacing the battery terminals with othercomponents is fixedly mounted in the internal cavity 43 of the firsthousing portion 12. The trigger switch assembly 50 is also pivotablycoupled to the first housing portion 12.

Likewise, the second housing portion 14 can be formed of a pair ofhousing shells 46, 47 that can cooperate to define another internalcavity 48. The second housing portion 14 is configured to receive thepowertrain assembly 49 which includes the motor 26, the transmission,and the output member 11. The power train assembly 49 can be mounted inthe internal cavity 48 such that a rotational axis of the output memberis disposed concentrically about the longitudinal axis of the secondhousing portion 14. One or more circuit boards 45 are also fixedlymounted in the internal cavity 48 of the second housing portion 14 (asshown in FIG. 14A). Components mounted to the circuit board may includethe rotational rate sensor 22, the microcontroller 24 as well as othercircuitry for operating the tool. The second housing portion 14 isfurther configured to support the rotation release mechanism 130.

With reference to FIGS. 3, 4, 12, 13, and 14, the rotary releasemechanism 130 can be mounted in either the first or second housingportions 12, 14. The release mechanism 130 comprises a lock bar assembly140 that engages with a set of locking features 132 associated with theother one of the first and second housing portions. In the exemplaryembodiment, the lock bar assembly 140 is slidably mounted inside thesecond housing portion 14. The lock bar assembly 140 is positionedpreferably so that it may be actuated by the thumb of a hand grippingthe first housing portion 12 of the tool. Other placements of the lockbar assembly and/or other types of lock bar assemblies are alsocontemplated. Further details regarding another lock bar assembly isfound in U.S. patent application Ser. No. 12/783,850 which was filed onMay 20, 2010 and is incorporated herein by reference.

The lock bar assembly 140 is comprised of a lock bar 142 and a biasingsystem 150. The lock bar 142 is further defined as a bar body 144, twopush members 148 and a pair of stop members 146. The push members 148are integrally formed on each end of the bar body 144. The bar body 144can be an elongated structure having a pocket 149 into which the biasingsystem 150 is received. The pocket 149 can be tailored to the particularconfiguration of the biasing system. In the exemplary embodiment, thebiasing system 150 is comprised of two pins 152 and a spring 154. Eachpin 152 is inserted into opposing ends of the spring 154 and includes anintegral collar that serves to retain the pin in the pocket. When placedinto the pocket, the other end of each pin protrudes through an apertureformed in an end of the bar body with the collar positioned between theinner wall of the pocket and the spring.

The stop members 146 are disposed on opposite sides of the bar body 144and integrally formed with the bar body 144. The stop members 146 can befurther defined as annular segments that extend outwardly from a bottomsurface of the bar body 144. In a locking position, the stop members 146are arranged to engage the set of locking features 132 that areintegrally formed on the shell assembly of the first housing portion 12as best seen in FIG. 14A. The biasing system 150 operates to bias thelock bar assembly 140 into the locking position. In this lockingposition, the engagement of the stop members 146 with the lockingfeatures 132 prevents the first housing portion from being rotated inrelation to the second housing portion.

To actuate the lock bar assembly 140, the push members 148 protrudethrough a push member aperture formed on each side of the second housingportion 14. When the lock bar assembly 140 is translated in eitherdirection by the tool operator, the stop members 146 slide out ofengagement with the locking features 132 as shown in FIG. 14B, therebyenabling the first housing portion to rotate freely in relation to thesecond housing portion. Of note, the push members 148 are offset fromthe center axis on which the first housing portion 12 and the secondhousing portion 14 rotate with respect to one another. This arrangementcreates an inertial moment that helps to rotate the second housingportion 14 in relation to the first housing portion 12. With a singleactuating force, the tool operator can release the lock bar assembly 140and continue rotating the second housing portion. The user can thencontinue to rotate the second housing portion. The user can thencontinue to rotate the second housing portion (e.g., 180 degrees) untilthe stop members re-engage the locking features. Once the stop members146 are aligned with the locking features, the biasing system 150 biasesthe lock bar assembly 140 into a locking position as shown in FIG. 14C.

An improved user-input method for the screwdriver 10 is proposed.Briefly, tool rotation is used to control rotation of the output member.In an exemplary embodiment rotational motion of the tool about thelongitudinal axis of the output member is monitored using the rotationalmotion sensor disposed in the power tool. The angular velocity, angulardisplacement, and/or direction of rotation can be measured and used as abasis for driving the output member. The resulting configurationimproves upon the shortcomings of conventional input schemes. With theproposed configuration, the control input and the resulting output occuras a rotation about the axis. This results in a highly intuitive controlsimilar to the use of a manual screwdriver. While the followingdescription describes rotation about the longitudinal axis of the outputmember, it is readily understood that the control input could berotational about a different axis associated with the tool. For example,the control input could be about an axis offset but in parallel with theaxis of the output member or even an axis askew from the axis of theoutput member. Further details regarding the control scheme may be foundin U.S. Patent Application No. 61/292,966 which was filed on Jan. 7,2010, and is incorporated herein by reference.

This type of control scheme requires the tool to know when the operatorwould like to perform work. One possible solution is a switch that thetool operator actuates to begin work. For example, the switch may be asingle pole, single throw switch accessible on the exterior of the tool.When the operator places the switch in an ON position, the tool ispowered up (i.e., battery is connected to the controller and otherelectronic components). Rotational motion is detected and acted upononly when the tool is powered up. When the operator places the switch inan OFF position, the tool is powered down and no longer operational.

In the exemplary embodiment, the tool operator actuates a trigger switchassembly 50 to initiate tool operation. With reference to FIGS. 5A-5C,the trigger switch assembly 50 is comprised primarily of an elongatedcasing 52 that houses at least one momentary switch 53 and a biasingmember 54, such as a spring. The elongated casing 52 is movably coupledto the first housing portion 12 in such a way that allows it totranslate and/or pivot about any point of contact by the operator. Forexample, if the tool operator presses near the top or bottom of theelongated casing 52, the trigger switch assembly 50 pivots as shown inFIGS. 5A and 5B, respectively. If the tool operator presses near themiddle of the elongated casing 52, the trigger switch assembly 50 istranslated inward towards the tool body as shown in FIG. 5C. In anycase, the force applied to the elongated casing 52 by the operator willdepress at least one of the switches from an OFF position to an ONposition. If there are two or more switches 53, the switches 53 arearranged electrically in parallel with each other (as shown in FIG. 7)such that only one of the switches needs to be actuated to power up thetool. When the operator releases the trigger, the biasing member 54biases the elongated casing 52 away from the tool, thereby returningeach of the switches to an OFF position. The elongated shape of thecasing helps the operator to actuate the switch from different grippositions. It is envisioned that the trigger switch assembly 50 may becomprised of more than two switches 53 and/or more than one biasingmember 54 as shown in FIGS. 6A-6C.

FIG. 16 illustrates an alternative trigger switch assembly 50, wherelike numerals refer to like parts. Elongated casing 52 is preferablycaptured by the first housing portion 12 so that it can only slide inone particular direction A. Elongated casing 52 may have ramps 52R.Ramps 52R engage cams 55R on a sliding link 55. Sliding link 55 iscaptured by the first housing portion 12 so that it can preferably onlyslide in along a direction B substantially perpendicular to direction A.

Sliding link 55 is preferably rotatably attached to rotating link 56.Rotating link 56 may be rotatably attached to the first housing portion12 via a post 56P.

Accordingly, when the user moves elongated casing 52 along direction A,ramps 52R move cams 55R (and thus sliding link 55) along direction B.This causes rotating link 56 to rotate and make contact with momentaryswitch 53, powering up the screwdriver 10.

Preferably, elongated casing 52 contacts springs 54 which bias elongatedcasing 52 in a direction opposite to direction A. Similarly, slidinglink 55 may contact springs 55S which bias sliding link 55 in adirection opposite to direction B. Also, rotating link 56 may contact aspring 56S that biases rotating link 56 away from momentary switch 53.

Persons skilled in the art will recognize that, because switch 53 can bedisposed away from elongated casing 52, motor 26 can be providedadjacent to elongated casing 52 and sliding link 55, allowing for a morecompact arrangement.

Persons skilled in the art will also recognize that, instead of havingthe user activating a discrete trigger assembly 50 in order to power upscrewdriver 10, screwdriver 10 can have an inherent switch assembly.FIGS. 17A-17B illustrate one such an alternative switch assembly, wherelike numerals refer to like parts.

Referring now to FIGS. 17A-17B for this embodiment, a power trainassembly 49 as shown in FIG. 4, which includes motor 26, the outputmember 11 and/or any transmission there between, is preferably encasedin a housing 71 and made to translate axially inside the first housingportion 12. A spring 72 of adequate stiffness biases the drivetrainassembly 71 forward in the tool housing. A momentary push-button switch73 is placed in axial alignment with the drivetrain assembly 71. Whenthe tool is applied to a fastener, a bias load is applied along the axisof the tool and the drivetrain assembly 71 translates rearwardcompressing the spring and contacting the pushbutton. In an alternativeexample, the drivetrain assembly remains stationary but a collar 74surrounding the bit is made to translate axially and actuate a switch.Other arrangements for actuating the switch are also contemplated.

When the pushbutton 73 is actuated (i.e., placed in a closed state), thebattery 28 is connected via power-regulating circuits to the rotationalmotion sensor, the controller 24, and other support electronics. Withreference to FIG. 7, the controller 24 immediately turns on a bypassswitch 34 (e.g., FET). This enables the tool electronics to continuereceiving power even after the pushbutton is released. When the tool isdisengaged from the fastener, the spring 72 again biases the drivetrainassembly 71 forward and the pushbutton 73 is released. In an exemplaryembodiment, the controller 24 will remain powered for a predeterminedamount of time (e.g., 10 seconds) after the pushbutton 73 is released.During this time, the tool may be applied to the same or differentfastener without the tool being powered down. Once the pushbutton 73 hasreleased for the predetermined amount of time, the controller 24 willturn off the bypass switch 34 and power down the tool. It is preferablethat there is some delay between a desired tool shut down and poweringdown the electronics. This gives the driver circuit time to brake themotor to avoid motor coasting. In the context of the embodimentdescribed in FIG. 7, actuation of pushbutton 73 also serves to reset(i.e., set to zero) the angular position. Powering the electronics maybe controlled by the pushbutton or with a separate switch. Batterieswhich are replaceable and/or rechargeable serve as the power source inthis embodiment, although the concepts disclosed herein as alsoapplicable to corded tools.

The operational state of the tool may be conveyed to the tool operatorby a light emitting diode 35 (LED) that will be illuminated while thetool is powered-up. The LED 35 may be used to indicate other toolconditions. For example, a blinking LED 35 may indicate when a currentlevel has been exceeded or when the battery is low. In an alternativearrangement, LED 35 may be used to illuminate a work surface.

In another alternative arrangement (as shown in FIG. 21), multiple LEDsmay be used to indicate the direction and speed of tool operation. Forexample, three side-by-side LEDs 35 can be lit consecutively one at atime from left to right when the output member 11 is rotating in aclockwise direction and from right to left when output member 11 isrotating in a counterclockwise direction. The duration of illumination,or blink rate, may indicate the speed of operation, where the longereach LED is lit, the slower the operation speed. When the direction ofrotation of output member 11 is reversed, the LEDs 35 should to reflectthis transition. For example, the LEDs 35 could all be litsimultaneously for a brief period when the tool's rotation passes backthrough the starting or reference point to indicate the change. If theuser does nothing else, the LEDs 35 might turn off or return to showingbattery life or some other status. If the user continues to rotate thetool in the opposite direction, the LEDs 35 would resume consecutiveillumination and blink rate based on direction and speed of rotation.Other alternative embodiments could include more or fewer LEDs used asdescribed above.

In another alternative arrangement, the direction of rotation of outputmember 11 might be indicated by one LED arrow. The arrow may changecolor based on speed, for example, from green to yellow to orange tored. The speed could also be indicated by the arrow's blink rate.

In this embodiment, the tool may be powered up but not engaged with afastener. Accordingly, the controller may be further configured to drivethe output member only when the pushbutton switch 73 is actuated. Inother words, the output member is driven only when the tool is engagedwith a fastener and a sufficient bias force is applied to the drivetrainassembly. Control algorithm may allow for a lesser bias force when afastener is being removed. For instance, the output member may be drivenin a reverse direction when a sufficient bias load is applied to thedrivetrain assembly as described above. Once the output member beginsrotating, it will not shut off (regardless of the bias force) until someforward rotation is detected. This will allow the operator to loosen ascrew and lower the bias load applied as the screw reverses out of thematerial without having the tool shut off because of a low bias force.Other control schemes that distinguish between a forward operation and areverse operation are also contemplated by this disclosure.

Non-contacting sensing methods may also be used to control operation ofthe tool. For example, a non-contact sensor 170 may be disposed on theforward facing surface 174 of the tool adjacent to the bit 178 as shownin FIG. 17C. The non-contact sensor 170 may be used to sense when thetool is approaching, being applied to, or withdrawing from a workpiece.Optic or acoustic sensors are two exemplary types of non-contactsensors. Likewise, an inertial sensor, such as an accelerometer, can beconfigured to sense the relative position or acceleration of the tool.For example, an inertial sensor can detect linear motion of the tooltowards or away from a workpiece along the longitudinal axis of thetool. This type of motion is indicative of engaging a workpiece with thetool or removing the tool after the task is finished. These methods maybe more effective for sensing joint completion and/or determining whento turn the tool off.

Combinations of sensing methods are also contemplated by thisdisclosure. For example, one sensing method may be used for startupwhile another is used for shutdown. Methods that respond to forceapplied to the workpiece may be preferred for determining when to startup the tool, while methods that sense the state of the fastener ormovement of the tool away from the application may be preferred fordetermining when to modify tool output (e.g., shut down the tool).

Components residing in the housing of the screwdriver 10 include arotational rate sensor 22, which may be spatially separated in a radialdirection from the output member as well as a controller 24 electricallyconnected to the rotational rate sensor 22 and a motor 26 as furtherillustrated schematically in FIG. 7. A motor drive circuit 25 enablesvoltage from the battery to be applied across the motor in eitherdirection. The motor 26 in turn drivably connects through a transmission(not shown) to the output member 11. In the exemplary embodiment, themotor drive circuit 25 is an H-bridge circuit arrangement although otherarrangements are contemplated. The screwdriver 10 may also include atemperature sensor 31, a current sensor 32, a tachometer 33 and/or a LED35. Although a few primary components of the screwdriver 10 arediscussed herein, it is readily understood that other components may beneeded to construct the screwdriver.

In an exemplary embodiment, rotational motion sensor 22 is furtherdefined as a gyroscope. The operating principle of the gyroscope isbased on the Coriolis effect. Briefly, the rotational rate sensor iscomprised of a resonating mass. When the power tool is subject torotational motion about the axis of the spindle, the resonating masswill be laterally displaced in accordance with the Coriolis effect, suchthat the lateral displacement is directly proportional to the angularrate. It is noteworthy that the resonating motion of the mass and thelateral movement of the mass occur in a plane which is orientedperpendicular to the rotational axis of the rotary member. Capacitivesensing elements are then used to detect the lateral displacement andgenerate an applicable signal indicative of the lateral displacement.Exemplary rotational rate sensors include the ADXRS150 or ADSRS300gyroscope devices commercially available from Analog Devices, or theISZ-650 or IXZ-2500 gyroscope devices commercially available fromInvenSense, Inc. It is readily understood that accelerometers,compasses, inertial sensors and other types of rotational motion sensorsare contemplated by this disclosure. It is also envisioned that thesensor as well as other tool components may be incorporated into abattery pack or any other removable pieces that interface with the toolhousing.

During operation, the rotational motion sensor 22 monitors rotationalmotion of the sensor with respect to the longitudinal axis of the outputmember 11. A control module implemented by the controller 24 receivesinput from the rotational motion sensor 22 and drives the motor 26 andthus the output member 11 based upon input from the rotational motionsensor 22. For example, the control module may drive the output member11 in the same direction as the detected rotational motion of the tool.As used herein, the term module may refer to, be part of, or include anApplication Specific Integrated Circuit (ASIC); an electronic circuit; acombinational logic circuit; a field programmable gate array (FPGA); aprocessor (shared, dedicated, or group) that executes code; othersuitable components that provide the described functionality; or acombination of some or all of the above, such as in a system-on-chip.The term module may include memory (shared, dedicated, or group) thatstores code executed by the processor, where code, as used above, mayinclude software, firmware, and/or microcode, and may refer to programs,routines, functions, classes, and/or objects.

Functionality for an exemplary control scheme 80 is further describedbelow in relation to FIG. 8A. During tool operation, angulardisplacement may be monitored by the controller 24 based upon inputreceived from the rotational motion sensor 22. In step 81, a starting orreference point (θ) is initialized to zero. Any subsequent angulardisplacement of the tool is then measured in relation to this reference.In an exemplary embodiment, the control scheme is implemented ascomputer executable instructions residing in a memory and executed by aprocessor of the controller 24.

At any point during operation, the user may wish to reset the startingor reference point (θ). For example, the user's wrist may be rotated 40°clockwise, and the user wants to reverse the direction of the tool'soperation. Instead of rotating back through the reference point andcontinuing to rotate to the left, the user may reset the reference pointto be the current position (in this example, 40° clockwise). Anysubsequent counterclockwise rotation from the new reference point willreverse the direction of the rotation of output member 11. In the secondexemplary embodiment (as shown in FIG. 20), where holding in the triggerswitch assembly 50 is how the tool remains in a powered-up state,releasing the trigger switch assembly 50 would reset the referencepoint. In an alternate embodiment, pressing the dedicated zero button210 (as shown in FIG. 21) would reset the reference point. Personsskilled in the art will recognize that other implementations can beenvisioned, such as requiring the zero button 210 to be pressed and heldfor a short period of time in order to prevent accidental zeroing.

Angular displacement of the tool is then monitored at step 82. In theexemplary embodiment, the angular displacement is derived from the rateof angular displacement over time or angular velocity (ω_(TOOL)) asprovided by the gyroscope. While the rotational rate sensor describedabove is presently preferred for determining angular displacement of thetool, it is readily understood that this disclosure is not limited tothis type of sensor. On the contrary, angular displacement may bederived in other manners and/or from other types of sensors. It is alsonoted that the signal from any rotational rate sensor can be filtered inthe analog domain with discrete electrical components and/or digitallywith software filters.

In this proposed control scheme, the motor is driven at differentrotational speeds depending upon the amount of rotation. For example,the angular displacement is compared at 84 to an upper threshold. Whenthe angular displacement exceeds an upper threshold θ_(UT) (e.g., 30° ofrotation), then the motor is driven at full speed as indicated at 85.The angular displacement is also compared at 86 to a lower threshold.When the angular displacement is less than the upper threshold butexceeds a lower threshold θ_(LT) (e.g., 5° of rotation), then the motoris driven at half speed as indicated at 87. It is readily understoodthat the control scheme may employ more or less displacement thresholdsas well as drive the motor at other speeds.

Angular displacement continues to be monitored at step 82. Subsequentcontrol decisions are based on the absolute angular displacement inrelation to the starting point as shown at 83. When the angulardisplacement of the tool remains above the applicable threshold, thenthe operating speed of the motor is maintained. In this way, continuousoperation of the tool is maintained until the tool is returned to itsoriginal position. In the exemplary embodiment, returning the tool toits original position means that the user returns the tool to within 10°to 15° of the original position, for example. This creates a rangearound the reference point that allows for a small margin of user error.The user is not required to find the exact reference point that was set.On the other hand, when the tool operator rotates the tool in theopposite direction and angular displacement of the tool drops below (isless than) the lower threshold, then the output of the tool is modifiedat 190. In an exemplary embodiment, the voltage applied to the motor isdiscontinued at 190, thereby terminating operation of the tool. In analternative embodiment, the speed at which the motor is driven isreduced to some minimal level that allows for spindle rotation at noload. Other techniques for modifying output of the tool are alsoenvisioned. Threshold values may include hysteresis; that is, the lowerthreshold is set at one value (e.g. six degrees) for turning on themotor but set at a different value (e.g., four degrees) for turning offthe motor, for example. It is also to be understood that only therelevant steps of the methodology are discussed in relation to FIG. 8A,but that other functionality may be needed to control and manage theoverall operation of the system.

A variant of this control scheme 80′ is shown in FIG. 8B. When theangular displacement is less than the upper threshold but exceeds alower threshold θ_(LT) (e.g., 5° of rotation), then the motor speed maybe set generally as a function of the angular displacement as indicatedat 87′. More specifically, the motor speed may be set proportional tothe full speed. In this example, the motor speed is derived from alinear function. It is also noted that more complex functions, such asquadratic, exponential or logarithmic functions, may be used to controlmotor speed. In another embodiment, the motor speed could beproportional to the displacement, velocity, acceleration, or acombination thereof (as shown in FIG. 8B, step 87′).

In either control scheme described above, direction of tool rotation maybe used to control the rotational direction of the output member. Inother words, a clockwise rotation of the tool results in a clockwiserotation of the output member, and a counterclockwise rotation of thetool results in a counterclockwise rotation of the output member.Alternatively, the tool may be configured with a switch that enables theoperator to select the rotational direction of the output member.

Persons skilled in the art will recognize that rotational motion sensor22 can be used in diverse ways. For example, the motion sensor 22 can beused to detect fault conditions and terminate operation. One such schemeis shown in FIG. 8C where, if the angular displacement is larger thanthe upper threshold θ_(U) (step 86), it could be advantageous to checkwhether the angular displacement exceeds on a second upper thresholdθ_(OT) (step 88). If such threshold is exceeded, then operation ofscrewdriver 10 can be terminated (step 89). Such arrangement isimportant in tools that should not be inverted or put in certainorientations. Examples of such tools include table saws, power mowers,etc.

Similarly, operation of screwdriver 10 can be terminated if motionsensor 22 detects a sudden acceleration, such as when a tool is dropped.

Alternatively, the control schemes in FIGS. 8A-8C can be modified bymonitoring angular velocity of output member 11 about the longitudinalaxis 8 instead of angular displacement. In other words, when the angularvelocity of rotation exceeds an upper threshold, such as 100°/second,then the motor is driven at full speed, whereas if the angular velocityis lower than the upper threshold but exceeds a lower threshold, such as50°/second, then the motor is driven at half speed.

Alternatively, the control schemes shown in FIGS. 8A-8C can be modifiedby monitoring angular acceleration instead of angular velocity. In otherwords, when the angular acceleration of rotation exceeds an upperthreshold, such as 100°/second per second, then the motor is driven atfull speed, whereas if the angular acceleration is lower than the upperthreshold but exceeds a lower threshold, such as 50°/second per second,then the motor is driven at half speed. Alternatively, a combination ofdisplacement, velocity, and/or acceleration could determine the controlscheme.

With reference to FIG. 18, a ratcheting control scheme 60 is alsocontemplated by this disclosure. During tool operation, the controllermonitors angular displacement of the tool at 61 based upon inputreceived from the rotational motion sensor 22. From angulardisplacement, the controller is able to determine the direction of thedisplacement at 62 and drive the motor 26 to simulate a ratchet functionas further described below.

In this proposed control scheme, the controller must also receive anindication from the operator at 63 as to which direction the operatordesires to ratchet. In an exemplary embodiment, the screwdriver 10 maybe configured with a switch that enables the operator to select betweenforward and reverse ratchet directions. Other input mechanisms are alsocontemplated.

When the forward ratchet direction is selected by the operator, thecontroller drives the motor in the following manner. When the operatorrotates the tool clockwise, the output member is driven at a higherratio than the rotation experienced by the tool. For example, the outputmember may be driven one or more full revolutions for each quarter turnof the tool by the operator. In other words, the output member isrotated at a ratio greater than one when the direction of rotationalmotion is the same as a user selected ratcheting direction as indicatedat 65. It may not be necessary for the user to select a ratchetdirection. Rather the control may make a ratcheting direction decisionbased on a parameter, for example, an initial rotation direction isassumed the desired forward direction.

On the other hand, when the operator rotates the tool counter clockwise,the output member is driven at a one-to-one ratio. Thus the outputmember is rotated at a ratio equal to one when the direction rotationalmotion is the opposite the user selected ratcheting direction asindicated at 67. In the case of the screwdriver, the bit and screw wouldremain stationary as the user twists the tool backward to prepare forthe next forward turn, thereby mimicking a ratcheting function.

The control schemes set forth above can be further enhanced by the useof multiple control profiles. Depending on the application, the tooloperator may prefer a control curve that gives more speed or morecontrol. FIG. 9 illustrates three exemplary control curves. Curve A is alinear control curve in which there is a large variable control region.If the user does not need fine control for the application and simplywants to run an application as fast as possible, the user would prefercurve B. In this curve, the tool output ramps up and obtains full outputquickly. If the user is running a delicate application, such as seatinga brass screw, the user would prefer curve C. In this curve, obtainingimmediate power is sacrificed to give the user a larger control region.In the first part of the curve, output power changes slowly; whereas,the output power changes more quickly in the second part of the curve.Although three curves are illustrated, the tool may be programmed withtwo or more control curves.

In one embodiment, the tool operator may select one of a set number ofcontrol curves directly with an input switch. In this case, thecontroller applies the control curve indicated by the input switch untilthe tool operator selects a different control curve.

In an alternative embodiment, the controller of the tool can select anapplicable control curve based on an input control variable (ICV) andits derivative. Examples of ICVs include displacement, velocity, andacceleration. The motor speed from the selected curve may be determinedby either the same or some other variable. For example, the controllermay select the control curve based on distance a trigger has traveledand the speed at which the user actuates the trigger switch. In thisexample, the selection of the control curve is not made until thetrigger has traveled some predetermined distance (e.g., 5% of the travelrange as shown in FIG. 9A) as measured from a starting position.

Once the trigger has traveled the requisite distance, the controllercomputes the speed of the trigger and selects a control curve from agroup of control curves based on the computed speed. If the user simplywants to drive the motor as quick as possible, the user will tend topull the trigger quickly. For this reason, if the speed of triggerexceeds some upper speed threshold, the controller infers that the userwants to run the motor as fast as possible and selects an applicablecontrol curve (e.g., Curve B in FIG. 9A). If the user is working on adelicate application and requires more control, the user will tend topull the trigger more slowly. Accordingly, if the speed of trigger isbelow some lower speed threshold, the controller infers the user desiresmore control and selects a different control curve (e.g., Curve C inFIG. 9A). If the speed of the trigger falls between the upper and lowerthresholds, the controller may select another control curve (e.g., CurveA in FIG. 9A). Curve selection could be (but is not limited to being)performed with every new trigger pull, so the user can punch the triggerto run the screw down, release, and obtain fine seating control with thenext slower trigger pull.

The controller then controls the motor speed in accordance with theselected control curve. In the example above, the distance travelled bythe trigger correlates to a percent output power. Based on the triggerdistance, the controller will drive the motor at the correspondingpercent output in accordance with the selected control curve. It isnoted that this output could be motor pulse width modulation, as in anopen loop motor control system, or it could be motor speed directly, asin a closed loop motor control system.

In another example, the controller may select the control curve based ona different input control variable, such as the angular distance thetool has been rotated from a starting point and its derivative, i.e.,the angular velocity at which the tool is being rotated. Similar totrigger speed, the controller can infer that the user wants to run themotor as fast as possible when the tool is rotated quickly and inferthat the user wants to run the motor slower when the tool is beingrotated slowly. Thus, the controller can select and apply a controlcurve in the manner set forth above. In this example, the percentage ofthe input control variable is computed in relation to a predefined rangeof expected rotation (e.g., +/−180 degrees). Selecting an applicablecontrol curve based on another type of input control variable land itsderivative is also contemplated by this disclosure.

It may be beneficial to monitor the input control variable and selectcontrol curves at different points during tool operation. For example,the controller may compute trigger speed and select a suitable controlcurve after the trigger has been released or otherwise begins travelingtowards its starting position. FIG. 9B illustrates three exemplarycontrol curves that can be employed during such a back-off condition.Curve D is a typical back off curve which mimics the typical ramp upcurve, such as Curve A. In this curve, the user passes through the fullrange of analog control before returning to trigger starting position.Curve E is an alternative curve for faster shutoff. If the trigger isreleased quickly, the controller infers that the user simply wants toshut the tool off and allows the user to bypass most of the variablespeed region. If the user backs off slowly, the controller infers thatthe user desires to enter the variable speed region. In this case, thecontroller may select and apply Curve F to allow the user better finishcontrol, as would be needed to seat a screw. It is envisioned that thecontroller may monitor the input control variable and select anapplicable control curve based on other types of triggering events whichoccur during tool operation.

Ramp up curves may be combined with back off curves to form a singleselectable curve as shown in FIG. 9C. In an exemplary application, theuser wishes to use the tool to drive a long machine screw and thusselects the applicable control curves using the input switch asdiscussed above. When the user pulls the trigger, the controller appliesCurve B to obtain full tool output quickly. When the user has almostfinished running down the screw, the user releases the trigger and thecontroller applies Curve F, thereby giving the user more control and theability to seat the screw to the desired tightness.

Selection of control curves may be based on the input control variablein combination with other tool parameters. For example, the controllermay monitor output torque using known techniques such as sensing currentdraw. With reference to FIG. 9D, the controller has sensed a slowtrigger release, thereby indicating the user desires variable speed forfinish control. If the controller further senses that output torque ishigh, the controller can infer that the user needs more output power tokeep the fastener moving (e.g., a wood screw application). In this case,the controller selects Curve G, where the control region is shiftedupward to obtain a usable torque. On the other hand, if the controllersenses that output torque is low, the controller can infer thatadditional output power is not needed (e.g., a machine screwapplication) and thus select Curve H. Likewise, the controller mayselect from amongst different control curves at tool startup based onthe sensed torque. Tool parameters other than torque may also be used toselect a suitable control curve.

Selection of control curves can also be based on a second derivative ofthe input control variable. In an exemplary embodiment, the controllercan continually compute the acceleration of the trigger. When theacceleration exceeds some threshold, the controller may select adifferent control curve. This approach is especially useful if the toolhas already determined a ramp up or back off curve but the user desiresto change behavior mid curve. For example, the user has pulled thetrigger slowly to allow a screw to gain engagement with a thread. Onceengaged, the user punches the trigger to obtain full output. Since thetool always monitors trigger acceleration, the tool senses that the useris finished with variable speed control and quickly sends the tool intofull output as shown in FIG. 9E.

Again, trigger input is used as an example in this scenario, but itshould be noted that any user input control, such as a gesture, could beused as the input control variable. For example, sensor 22 can detectwhen the user shakes a tool to toggle between control curves or evenoperation modes. For example, a user can shake a sander to togglebetween a rotary mode and a random orbit mode. In the examples set forthabove, the controller controls the motor speed in accordance with thesame input control variable as is used to select the control curve. Itis envisioned that the controller may control the motor speed with aninput control variable that differs from the input control variable usedto select the control curve. For example, motor speed may be set basedon displacement of the trigger; whereas, the control curve is selectedin accordance with the velocity at which the trigger is actuated.

Referring to FIG. 7, the screwdriver 10 includes a current sensor 32 todetect current being delivered to the motor 26. It is disadvantageousfor the motor of the tool to run at high current levels for a prolongedperiod of time. High current levels are typically indicative of hightorque output. When the sensed current exceeds some predefinedthreshold, the controller is configured to modify tool output (e.g.,shut down the tool) to prevent damage and signal to the operator thatmanually applied rotation may be required to continue advancing thefastener and complete the task. The tool may be further equipped with aspindle lock. In this scenario, the operator may actuate the spindlelock, thereby locking the spindle in fixed relation to the tool housing.This causes the tool to function like a manual screwdriver.

Referring to FIG. 8D, in a related embodiment, in embodiments where thepower tool described above has a spindle lock or self-locking gears, thecurrent sensor and controller may control the motor so that, at hightorque levels, the power tool can be used as a simulated manual,ratcheting screwdriver. At step 802, during operation of the power toolaccording to one of the control schemes in FIGS. 8A-8C, the controllermonitors a current sense signal (I_(SENSE)) from the current sensor,where I_(SENSE) indicates the amount of current being delivered to themotor. At step 804, the controller compares I_(SENSE) to a predeterminedreference value I_(MAX), which indicates the maximum current that may bedelivered to the motor. I_(MAX) can be stored in memory and can be afixed value or a user-selectable value. In many applications I_(SENSE)and I_(MAX) may correlate or be related to the output torque of thedrive shaft. At step 806, if I_(SENSE) does not exceed I_(MAX), then thecontroller continues to operate the power tool according to one of thecontrol schemes set forth in FIGS. 8A-8C.

At step, 808, if I_(SENSE) exceeds I_(MAX) for a predetermined amount oftime, then the controller causes a reduced, but non-zero, amount ofpower (LOW-PWM) to be delivered to the motor in the direction that themotor and output shaft were previously being driven. This LOW-PWM is lowenough so that the LOW-PWM signal cannot overcome the output torquebeing encountered by the tool shaft. For example, if I_(SENSE) indicatesthat the current being delivered to the motor is greater thanapproximately 20 amps (e.g., approximately 25 amps) for at least 200 ms,then the controller operates to deliver a LOW-PWM signal to the motorthat is less than approximately 20% (e.g., approximately 15%) of themaximum PWM duty cycle that was previously being delivered to the motorduring normal operation. Therefore, if the user continues to rotate thetool housing in the driving direction of the motor, the user will needto manually apply a torque that is greater than the output torque, sothat the tool functions as a manual screwdriver. If the user rotates thetool housing in the opposite direction, the LOW-PWM signal will make theoutput shaft remain effectively stationary relative to the workpiece,thus preventing rotating a fastener in the opposite direction. Thus, thepower tool will act as a ratcheting screwdriver while in the LOW-PWMmode of operation. It should be understood that the control scheme ofFIG. 8D is not limited for use with the inertia control schemes of FIGS.8A-8C, but can also be used with a more traditional electric power toolor screwdriver that is operated by a switch or trigger.

For the above-described inertia-controlled tools, there may be noindication to the user that the tool is operational, for example, whenthe user depresses the trigger switch assembly 50 but does not rotatethe tool. Accordingly, the screwdriver 10 may be further configured toprovide a user-perceptible output when the tool is operational.Providing the user with haptic feedback is one example of auser-perceptible output. The motor driven circuit 25 may be configuredas an H-bridge circuit as noted above and in FIG. 7. The H-bridgecircuit is used to selectively open and close pairs of field effecttransistors (FETs) to change the current flow direction and thereforethe rotational direction of the motor. By quickly transitioning back andforth between forward and reverse, the motor can be used to generate avibration perceptible to the tool operator. The frequency of a vibrationis dictated by the time span for one period and the magnitude of avibration is dictated by the ratio of on time to off time as shown inFIG. 10. Other schemes for vibrating the tool also fall within thebroader aspects of this disclosure.

Within the control schemes presented in FIGS. 8A-8C, the H-bridgecircuit 25 (as seen in FIG. 7) may be driven in the manner describedabove before the angular displacement of the tool reaches the lowerthreshold. Consequently, the user is provided with haptic feedback whenthe spindle is not rotating. It is also envisioned that user may beprovided haptic feedback while the spindle is rotating. For example, thepositive and negative voltage may be applied to the motor with animbalance between the voltages such that the motor will advance ineither a forward or reverse direction while still vibrating the tool. Itis understood that haptic feedback is merely one example of aperceptible output and other types of outputs also are contemplated bythis disclosure.

Vibrations having differing frequencies and/or differing magnitudes canalso be used to communicate different operational states to the user.For example, the magnitude of the pulses can be changed proportionallyto speed to help convey where in a variable-speed range the tool isoperating. So as not to limit the total tool power, this type offeedback may be dropped out beyond some variable speed limit (e.g., 70%of maximum speed). In another example, the vibrations may be used towarn the operator of a hazardous tool condition. Lastly, the hapticfeedback can be coupled with other perceptible indicators to helpcommunicate the state of the tool to the operator. For instance, a lighton the tool may be illuminated concurrently with the haptic feedback toindicate a particular state.

Additionally, haptic feedback can be used to indicate that the outputmember has rotated 360°, or that a particular desired torque setting hasbeen achieved.

In another aspect of this invention, an automated method is provided forcalibrating a gyroscope residing in the screwdriver 10. Gyroscopestypically output a sensed-analog voltage (Vsense) that is indicative ofthe rate of rotation. Rate of rotation can be determined by comparingthe sensed voltage to a reference voltage (e.g.,rate=(Vsense−Vref)/scale factor). With some gyroscopes, this referencevoltage is output directly by the gyroscope. In other gyroscopes, thisreference voltage is a predetermined level (i.e., gyroscope supplyvoltage/2) that is set as a constant in the controller. When the sensedvoltage is not equal to the reference voltage, rotational motion isdetected. When the sensed voltage is equal to the reference voltage, nomotion is occurring. In practice, there is an offset error (ZRO) betweenthe two voltages (i.e., ZRO=Vsense−Vref). This offset error can becaused by different variants, such as mechanical stress on a gyroscopeafter mounting to a PCT or an offset error in the measuring equipment.The offset error is unique to each gyroscope but should remain constantover time. For this reason, calibration is often performed after a toolis assembled to determine the offset error. The offset error can bestored in memory and used when calculating the rotational rate (i.e.,rate−(Vsense−Vref-ZRO/scale).

Due to changes in environmental conditions, it may become necessary torecalibrate the tool during the course of tool use. Therefore, it isdesirable for the tool to be able to recalibrate itself in the field.FIG. 11 illustrates an exemplary method for calibrating the offset errorof the gyroscope in the tool. In an exemplary embodiment, the method isimplemented by computer-executable instructions executed by a processorof the controller 24 in the tool.

First, the calibration procedure must occur when the tool is stationary.This is likely to occur once an operation is complete and/or the tool isbeing powered down. Upon completing an operation, the tool will remainpowered on for a predetermined amount of time. During this time period,the calibration procedure is preferably executed. It is understood thatthe calibration procedure may be executed at other times when the toolis or is likely to be stationary. For example, the first derivative ofthe sensed voltage measure may be analyzed to determine when the tool isstationary.

The calibration procedure begins with a measure of the offset error asindicated at 114. After the offset error is measured, it is compared toa running average of preceding offset error measurements (ZROavg). Therunning average may be initially set to the current calibration valuefor the offset error. The measured offset error is compared at 115 to apredefined error threshold. If the absolute difference between themeasured offset error and the running average is less than or equal tothe predefined offset error threshold, the measured offset error may beused to compute a newly-calibrated offset error. More specifically, themeasurement counter (calCount) may be incremented at 116 and themeasured offset error is added to an accumulator (ZROaccum) at 117. Therunning average is then computed at 118 by dividing the accumulator bythe counter. A running average is one exemplary way to compute thenewly-calibrated offset error.

Next, a determination is made as to whether the tool is stationaryduring the measurement cycle. If the offset error measurements remainconstant or nearly constant over some period of time (e.g., 4 seconds)as determined at 119, the tool is presumed to be stationary. Before thistime period is reached, additional measurements of the offset error aretaken and added to the running average so long as the difference betweeneach offset error measurement and the running average is less than theoffset error threshold. Once the time period is reached, the runningaverage is deemed to be a correct measurement for the offset error. Therunning average can be stored in memory at 121 as the newly-calibratedoffset error and subsequently used by the controller during thecalculations of the rotational rate.

When the absolute difference between the measured offset error and therunning average exceeds the predefined offset error threshold, the toolmust be rotating. In this case, the accumulator and measurement counterare reset as indicated at steps 126 and 127. The calibration proceduremay continue to execute until the tool is powered down or some othertrigger ends the procedure.

To prevent sudden erroneous calibrations, the tool may employ alonger-term calibration scheme. The method set forth above determineswhether or not there is a need to alter the calibration value. Thelonger-term calibration scheme would use a small amount of time (e.g.,0.25 s) to perform short-term calibrations, since errors would not becritical if no rotational motion is sensed in the time period. Theaveraged ZRO would be compared to the current calibration value. If theaveraged ZRO is greater than the current calibration value, thecontroller would raise the current calibration value. If the averagedZRO is less than the current calibration value, the controller wouldlower the current calibration value. This adjustment could either beincremental or proportional to the difference between the averaged valueand the current value.

Due to transmission backlash, the tool operator may experience anundesired oscillatory state under certain conditions. While the gears ofa transmission move through the backlash, the motor spins quickly, andthe user will experience like reactionary torque. As soon as thebacklash is taken up, the motor suddenly experiences an increase in loadas the gears tighten, and the user will quickly feel a strongreactionary torque as the motor slows down. This reactionary torque canbe strong enough to cause the tool to rotate in the opposite directionas the output spindle. This effect is increased with a spindle locksystem. The space between the forward and reverse spindle locks actssimilarly to the space between gears, adding even more backlash into thesystem. The greater the backlash, the greater amount of time the motorhas to run at a higher speed. The higher a speed the motor achievesbefore engaging the output spindle, the greater the reactionary torque,and the greater the chance that the body of the tool will spin in theopposite direction.

While a tool body's uncontrolled spinning may not have a large effect ontool operation for trigger-controlled tools, it may have a prominent anddetrimental effect for rotation-controlled tools. If the user controlstool output speed through the tool-body rotation, any undesired motionof the tool body could cause an undesired output speed. In the followingscenario, it can even create an oscillation effect. The user rotates thetool clockwise in an attempt to drive a screw. If there is a greatamount of backlash, the motor speed will increase rapidly until thebacklash is taken up. If the user's grip is too relaxed at this point,the tool will spin uncontrolled in the counterclockwise direction. Ifthe tool passes the zero rotation point and enters into negativerotation, the motor will reverse direction and spin counterclockwise.The backlash will again be taken up, eventually causing the tool body tospin uncontrolled in the clockwise direction. This oscillation oroscillatory state may continue until tool operation ceases.

FIG. 15 depicts an exemplary method of preventing such an oscillatorystate in the screwdriver 10. For illustration purposes, the method workscooperatively with the control scheme described in relation to FIG. 8A.It is understood that the method can be adapted to work with othercontrol schemes, including those set forth above. In an exemplaryembodiment, the method is implemented by controller 24 in the tool.

Rotational direction of the output spindle is dictated by the angulardisplacement of the tool as discussed above. For example, a clockwiserotation of the tool results in clockwise rotation of the output member.However, the onset of an oscillatory state may be indicated when toolrotation occurs for less than a predetermined amount of time beforebeing rotated in the opposing direction. Therefore, upon detectingrotation of the tool, a time is initiated at 102. The timer accrues theamount of time the output member has been rotating in a given direction.Rotational motion of the tool and its direction are continually beingmonitored as indicated at 103.

When the tool is rotated in the opposite direction, the method comparesthe value of the timer to a predefined threshold (e.g., 50 ms) at 104.If the value of the timer is less than the threshold, the onset of anoscillatory state may be occurring. In an exemplary embodiment, theoscillatory state is confirmed by detecting two oscillations although itmay be presumed after a single oscillation. Thus, a flag is set at 105to indicate the occurrence of a first oscillation. If the value of thetimer exceeds the threshold, the change in rotational direction ispresumed to be intended by the operator and thus the tool is not in anoscillating state. In either case, the timer value is reset andmonitoring continues.

In an oscillatory state, the rotational direction of the tool will againchange as detected at 103. In this scenario, the value of the timer isless than the threshold and the flag is set to indicate the precedingoccurrence of the first oscillation. Accordingly, a corrective actionmay be initiated as indicated at 107. In an exemplary embodiment, thetool may be shut down for a short period of time (e.g., ¼ second),thereby enabling the user to regain control of the tool before operationis resumed. Other types of corrective actions are also contemplated bythis disclosure. It is envisioned that the corrective action may beinitiated after a single oscillation or some other specific number ofoscillations exceeding two. Likewise, other techniques for detecting anoscillatory state fall within the broader aspects of this disclosure.

In another arrangement, the tool may be configured with self-lockingplanetary gear set 90 disposed between the output member 11 and a driveshaft 91 of the motor 26. The self-locking gear set could include anyplanetary gear set which limits the ability to drive the sun gearthrough the ring gear and/or limits the ability of the spindle toreverse. This limiting feature could be inherent in the planetary gearset or it could be some added feature such as a sprag clutch or a oneway clutch. Referring to FIGS. 19A and 19B, one inherent method to limitthe ability of a ring gear to back drive a sun gear 92 is to add anadditional ring gear 93 as the output of the planetary gear set 94 andfix the first ring gear 95. By fixing the first ring gear 95, power istransferred through the sun gear 92 into the planetary gear set 94 intothe second (unfixed, out) ring gear 93.

When torque is applied back through the output ring gear 93 into theplanetary gear set 94, the internal gear teeth on the output ring gearare forced into engagement with the corresponding teeth on the planetarygear set 94. The teeth on the planetary gear set 94 are then forced intoengagement with the corresponding teeth on the fixed ring gear. Whenthis happens, the forces on the planetary gears' teeth are balanced bythe forces acting through the output ring gear 93 and the equal andopposite forces acting through the fixed ring gear 95 as seen in FIG.19B. When the forces are balanced, the planetary gear is fixed and doesnot move. This locks the planetary gear set and prevents torque frombeing applied to the sun gear. Other arrangements for the self-lockinggear set are also contemplated by this disclosure.

The advantage of having a self-locking planetary gear set is that whenthe motor is bogged down at high torque levels during twistingoperations such as, but not limited to, threaded fasteners, the tooloperator can overcome the torque by twisting the tool. This extra torqueapplied to the application from the tool operator is counteracted by theforces within the self-locking planetary gear set, and the motor doesnot back drive. This allows the tool operator to apply additional torqueto the application.

In this arrangement, when the sensed current exceeds some predefinedthreshold, the controller may be configured to drive the motor at someminimal level that allows for spindle rotation at no load. This avoidsstressing the electronics in a stall condition but would allow forratcheting at stall. The self-locking planetary gears would still allowthe user to override stall torque manually. Conversely, when the userturns the tool in the reverse direction to wind up for the next forwardturn, the spindle rotation would advance the bit locked in thescrewhead, thereby counteracting the user's reverse tool rotation.

With reference to FIG. 20, a second exemplary power screwdriver isindicated generally by reference number 10′. This embodiment allows theuser to hold the screwdriver 10′ in the palm of the user's hand andactuate the trigger switch assembly 50′ with the palm of the user'shand, most preferably the area of the palm that forms the base of theuser's thumb. In this embodiment, the tool operator actuates the triggerswitch assembly 50′ to initiate tool operation. Given the orientation ofthe screwdriver 10′ in the palm of the user's hand, it should berecognized that the trigger switch assembly 50′ is actuated and remainsdepressed just by holding the screwdriver 10′. This allows for naturaland intuitive use, where the user can simply hold the screwdriver 10′and turn it.

With reference to FIGS. 5A-5C and 20, the trigger switch assembly 50′ issubstantially similar to the trigger switch assembly 50. The triggerswitch assembly 50′ is comprised primarily of an elongated casing 52that houses at least one momentary switch 53 and a biasing member 54,such as a spring. The elongated casing 52 is movably coupled to housing200 in such a way that allows it to translate and/or pivot about anypoint of contact by the operator. For example, if the tool operatorpresses near the top or bottom of the elongated casing 52, the triggerswitch assembly 50′ pivots as shown in FIGS. 5A and 5B, respectively. Ifthe tool operator presses near the middle of the elongated casing 52,the trigger switch assembly 50′ is translated inward towards the toolbody as shown in FIG. 5C. In any case, the force applied to theelongated casing 52 by the operator will depress at least one of theswitches from an OFF position to an ON position. If there are two ormore switches 53, the switches 53 are arranged electrically in parallelwith each other (as shown in FIG. 7) such that only one of the switchesneeds to be actuated to power up the tool. When the operator releasesthe trigger, the biasing member 54 biases the elongated casing 52 awayfrom the tool, thereby returning each of the switches to an OFFposition. The elongated shape of the casing helps the operator toactuate the switch from different grip positions. It is envisioned thatthe trigger switch assembly 50′ may be comprised of more than twoswitches 53 and/or more than one biasing member 54 as shown in FIGS.6A-6.C. This embodiment otherwise functions as described for theprevious embodiment.

With reference to FIG. 21, a third exemplary power screwdriver isindicated generally by reference number 10″. In this embodiment, thetool operator actuates the trigger switch assembly 50″ with the user'sindex finger to power up the screwdriver 10″. The trigger switchassembly 50″ functions as an ON/OFF switch. Once the user presses andreleases the trigger switch assembly 50″, the screwdriver 10″ is in anON state (i.e., the battery is connected to the controller and otherelectronic components). Rotational motion is detected and acted upononly when the tool is powered up. When the operator places the switch inan OFF position, the tool is powered down and is no longer operational.The screwdriver 10″ remains in the ON state until the user turns it offby pressing and releasing the trigger switch assembly 50″ again. It isalso contemplated that the screwdriver 10″ will automatically shut offafter a period of inactivity, and the trigger switch assembly 50″ may beimplemented in other ways.

Output member 11 rotates around longitudinal axis 8′ based on angulardisplacement as described above. In other words, the user rotates thescrewdriver 10″ to drive output member 11. In this third embodiment, azero button 210 allows the user to reset the starting or reference pointas previously described.

The tool may be further configured with a reaming tool 214 disposedbetween the second housing portion 14 and the output member 11. Forexample, a user may wish to refine a hole drilled using the tool orremove burrs from the cut end of a piece of conduit. This embodiment hastwo modes of operation: the motor 26 either drives the output member 11or the reaming tool 214. In one arrangement, the mode is selectedmanually by the user as shown in FIGS. 22A-22B and described below. Inanother arrangement, the mode is selected by applying either the outputmember 11 or the reaming tool 214 to a workpiece in order to usescrewdriver 10″ as a screwdriver or a reamer, respectively, as shown inFIGS. 23A-23B and described below. Other means for selecting the mode ofoperation are also contemplated by this disclosure.

Other reaming tool variations are contemplated. In an alternativeembodiment, the reaming tool would oscillate. For example, the user'swrist remains rotated clockwise, and the reaming tool rotates in aclockwise direction for a short time period, reverses direction for ashort time period, repeating until operation is terminated. In anotheralternative embodiment, the reaming tool would have a pulse mode. If thedrive signal is pulsed, a spike in the torque output might facilitateovercoming a burr. In still another alternative embodiment, the powertool could have multiple gears associated with it. At lower speeds,higher torque could be achieved while at higher speeds, lower torquewould be sufficient for driving screws, for example.

FIGS. 22A-22B show an exemplary clutch mechanism for selectivelyengaging the reaming tool 214 (to operate screwdriver 10″ as a reamer)or the output member 11 (to operate screwdriver 10″ as a screwdriver).It is to be understood that the representation of the reaming tool 214in FIGS. 22A-22B has been simplified from its depiction in FIG. 21 inorder to more clearly convey the mode switching.

In this exemplary embodiment, the user rotates a collar 240 between twopositions to select the mode of operation. It should be understood thatthis collar could also be implemented to translate between the twopositions while remaining rotationally fixed. The collar 240 is attachedto a grounding ring 228. When the grounding ring 228 is in the rearwardposition as shown in FIG. 22A, the grounding ring 228 engages a planetcarrier 236 and prevents it from rotating. In this configuration, themotor drives the planets 237 to rotate about the pins of the planetcarrier 236, causing the ring gear 232 to rotate. This drives thereaming tool 214 while the output member 11 remains fixed, and as such,screwdriver 10″ operates as in reamer mode. When the grounding ring 228is in the forward position as shown in FIG. 22B, the planet carrier 236is free to rotate, and the ring gear 232 is fixed. In thisconfiguration, the motor drives the planets 237 which in turn drives theoutput member 11, and as such, screwdriver 10″ operates in screwdrivermode. It is envisioned that in an alternative embodiment, the ring gear232 and the planet carrier 236 may be fixed to one another and free torotate at the same time.

FIGS. 23A and 23B illustrate another exemplary clutch mechanism forselecting the mode of operation. In this embodiment, a dog type clutch238 is used to selectively engage the reaming tool 214. It is to beunderstood that the representation of the reaming tool 214 in FIGS.23A-23B has been simplified from its depiction in FIG. 21 in order tomore clearly convey the mode switching.

In this arrangement, screwdriver 10″ operates as a screwdriver as shownin FIG. 23A unless the user applies the reaming tool 214 to a workpiece230. If no force is applied to the reaming tool, the dog clutch 238 isnot engaged, and the output member 11 is free to rotate. To operatescrewdriver 10″ as a reamer, the user applies the reaming tool 214 to aworkpiece 230. This bias load applies a force to the compression springs234, as shown in FIG. 23B. This engages the dog clutch 238, which causesthe reaming tool 214 to rotate with the output member 11. Thisembodiment otherwise functions the same as the other embodimentsdiscussed above.

Referring to FIGS. 24-27, in other embodiments, a reaming attachment 300may be coupled to an output shaft 312 of a power tool 310. The powertool 310 may be similar to the above-described screwdriver 10 that isdriven according to rotation of the tool housing as sensed by arotational motion sensor. In other embodiments, the power tool 310 maybe an ordinary power drill, power driver, or power screwdriver that isdriven according to actuation of an on-off power switch or a variablespeed trigger switch.

Referring to FIG. 24, the reaming attachment 300 includes a drivingshaft 302 integral with the output shaft 312 for rotation with theoutput shaft 312 about a longitudinal axis X. In the embodiment of FIG.24, the driving shaft 302 is permanently attached to the output shaft312 of the power tool 310. However, referring to FIG. 27, in otherembodiments, a similar reaming attachment 300′ may include a drivingshaft 302′ having a hex fitting 303′ that can be removably coupled to anoutput shaft of a power tool, e.g., by a quick-release tool holder, achuck, or a hex tool holder. In other embodiments, a driving shaft canbe removably coupled to an output shaft, e.g., by a threaded connection,a friction fit coupling, a snap-fit connector, and/or a bayonetconnection.

The driving shaft 302 non-rotationally carries a screwdriving portion320 and a reaming portion 330. Unlike the embodiments of FIGS. 22A-23B,the screwdriving portion 320 and the reaming portion 330 always rotatetogether with the driving shaft 302 about the axis X, and thus togetherwith the output shaft 312 of the power tool 310.

The reaming portion 330 includes a front body portion 332 and a rearbody portion 340 that are non-rotationally carried by the driving shaft302. The front body portion 332 has a stepped configuration with aplurality of cylindrical steps 334 that increase in diameter from frontto rear. Adjacent cylindrical steps 334 are connected by frustroconicalsurfaces 336. The rear body portion 340 comprises a generallycylindrical disc 342. The rear body portion 340 is axially fixed to thedriving shaft 302 and abuts the housing front end of the power tool 310.The front body portion 332 is axially moveable relative to the drivingshaft 302 and is biased away from the rear body portion 340 by acompression spring 344 disposed between the front body portion 332 andthe rear body portion 340.

The front and rear body portions 332, 340 have radial slots 346, 348,respectively, that extend in an axial direction. Removably received inthe axial slots 346, 348 is a reaming blade 350. The blade 350 has arear end 352 axially fixed to the rear body portion 340, and a workingend 354 that remains stationary relative to the driving shaft 302 whenthe front body portion 340 moves axially. The working end 354 has astepped configuration with a plurality of hook shaped cutting surfaces356, each having a diameter corresponding to one of the cylindricalsteps 334 on the front body portion 332.

In operation, when the power tool 310 causes the output shaft 312 torotate about its axis, the output shaft 312 causes the driving shaft302, screwdriving portion 320, and the front and rear bodies 332, 340 ofthe reaming portion 340 to rotate simultaneously about the longitudinalaxis X. As shown in FIG. 25, the reaming attachment 320 may be used todrive a fastener 360 into a workpiece W (as shown in FIG. 25). Ascrewdriving bit 362 is inserted into the bit holding portion 322. Thefront body 332 remains biased in its forward-most position, so that thecutting surfaces 356 of the blade 350 are not exposed. The driving shaft302 causes the screwdriving bit 362 to rotate to drive the screw 360into the workpiece.

As shown in FIGS. 26A and 26B, the reaming attachment 230 may also beused to ream the edge 370 of a pipe P to remove burrs or shavings. Asshown in FIG. 26A, the front body is inserted into the pipe P until oneof the stepped cylindrical surfaces 334 or conical surfaces 336 abutagainst the edge 370 of the pipe P. Referring to FIG. 26B, as furtheraxial bias is applied to the power tool 310, the front body 332 retractsrearward in a direction R against the force of spring 344. Thisretraction of the front body 332 causes the cutting surfaces 356 of theblade 350 to be exposed. One of the hook shaped cutting surfaces 356hooks around the edge 370 of the blade. As the driving shaft 302rotates, the cutting surface 356 rotates to remove material from theedge 370 of the pipe P. When the reaming is complete, the front portion332 is removed from the pipe P and moves axially forward opposite thedirection R, to cause apparent retraction of the cutting surfaces 356.

Referring to FIGS. 25A-25C, the screwdriving portion 320 includes a bitholding portion 322 formed at the front end of the driving shaft 302.The bit holding portion 322 is formed with an internal bore 324configured to retain a bit 362, such a screwdriving bit, for driving afastener (e.g., screw 360) into a workpiece W. The bit holding portion322 may include a bit retention assembly for holding the bit 362 in theinternal bore 324. For example, referring to FIGS. 25B and 25C, a bitretention assembly 380 includes a shaft 412 having a sidewall 413defining the internal bore 324 in the form of a polygonal (e.g.,hexagonal) cavity.

The stepped front body 332 of the reamer portion 340 functions as anactuator sleeve and is disposed around a first end 424 of the shaft 412.The stepped front body 332 engages a retainer 426 (e.g., a ball) that isreceived in a groove opening 428 of the sidewall 413 of the shaft 412.In inside wall of the stepped front body 332 includes an internal rampportion 432 and an internal cylindrical portion 433 that each canselectively abut the retainer ball 426. A retainer spring 430substantially surrounds the shaft 412 and biases the retainer ball 426in a forward direction (best shown in FIG. 25C). The retainer spring 430can be a helical compression spring having a helix portion 430 a andending at a bend portion that transitions to an inwardly projectingportion that is received at least partially in the groove opening 428 tobias the retainer 426 in a forward direction toward the front end 424 ofthe shaft 412. A rearward portion of the retainer spring 430 is disposedagainst a forward facing shoulder 412 a of the shaft 412.

An actuator spring 436 biases the stepped front body 332 in a rearwarddirection relative to the first end 424 of the shaft 412. A retainerclip 440 is received in a recessed groove 442 in the first end 424 ofthe shaft 412 for supporting a washer 444 against a forward end of theactuator spring 436. A second end of the actuator spring 436 is receivedagainst an interior shoulder portion 445 of the stepped front body 332in order to bias the stepped front body 332 in a rearward directionrelative to the first end 424 of the shaft 412.

In its rest position, the stepped front body 332 is positioned over thebit holding portion 322 so that the inner cylindrical portion 433 abutsthe ball 426 and biases the ball radially inwardly. When the bit 362 isinserted into the internal bore 324, the end of the bit 362 engages theball 426, pushing the ball 426 rearward against the force of theretainer spring 430. As the ball 426 moves rearward in the grooveopening 428, it also moves radially outward along the internal ramp 432,providing clearance for further insertion of the bit. Once the bit 362is fully inserted into the bore 324, the spring 430 causes the ball 426to move forward and radially inward to engage a notch or groove 363 inthe bit 362. The inner cylindrical surface 433 now pushes the ball 462radially inward to retain the bit 362 in the bore 324.

In order to release the bit 326 from the bit retention device 380, thestepped front body 332 is pulled in a forward direction against theforce of the spring 436. This causes the ramp 432 to be axially alignedwith the ball 452 so that the ball can move radially outward along thesurface of the ramp. Thus, the ball no longer tightly engages the groove363 in the bit, enabling the bit 362 to be removed from the bore 324.

In other embodiments, the bit retention device 380 may include a plungerfor ejecting the bit from the bore when the ball is not engaging thebit. In yet other embodiments, other types of bit retention mechanismsmay be used, such as, for example, a hog ring, a retention clip, or amagnet. Examples of other retention mechanisms can be found, e.g., inU.S. Patent App. Pub. No. 2012/0326401, which is incorporated byreference. In further embodiments, the driving shaft 302 may be formedwith a screwdriving or nut driving head portion, or another type ofrotational driving implement.

With reference to FIGS. 28A and 28B, in another exemplary embodiment, arotary power tool in the form of a ratchet wrench 510 may include theabove or below described embodiments of an improved user input control.Exemplary components and features of the ratchet wrench 510 aredescribed below. While the following description is provided withreference to a ratchet wrench 510, it should be readily understood toone of ordinary skill in the art that the broader aspects of the presentdisclosure are applicable to other types of power tools that have anoutput axis at an angle to a rotatable axis of the motor, including butnot limited to other power tools that have an elongated housing alignedperpendicularly to a rotational axis of an output member of the tool,e.g., a right angle drill or right angle screwdriver.

The ratchet wrench 510 is a right angle socket wrench and includes anelongated housing 512 having a longitudinal axis 509. The housing 512may be formed from two or more housing shells that cooperate to definean internal cavity. The housing 512 is configured to receive a motor526, a transmission 515 coupled to an output of the motor 526, and anintermediate rotatable shaft 519 rotatably coupled to an output of thetransmission 515. Coupled to the housing 512 is a ratcheting head 521having a ratcheting mechanism 523 coupled to an output of theintermediate shaft 519, and an output member or drive shaft 511, wherethe rotational axis 508 of the output member 511 is arranged generallyperpendicular to the longitudinal axis 509 of the housing 512.

The drive shaft 511 is configured to rotate about its rotational axis508 in a ratcheting manner in one direction (either clockwise orcounterclockwise) when the intermediate shaft 519 is rotated by themotor in either a clockwise or a counterclockwise direction. Theratcheting head 521 further includes a mechanical switch 525 thatenables the rotational direction of the output shaft 511 to be switchedbetween ratcheting in the clockwise direction and ratcheting in thecounterclockwise direction, regardless of the direction of rotation ofthe intermediate shaft. Further details regarding operation of theratcheting head can be found in prior art ratcheting wrenches,including, e.g., U.S. Pat. Nos. 6,490,953 and 7,793,568, which arehereby incorporated by reference. In the alternative, the ratchetinghead may have other types of transmission mechanisms that do notratchet, but that only change the direction of rotation by a rightangle, right angle or bevel gears, as will be understood by one ofordinary skill in the art.

The output member 511 may has a polygonal shape (e.g., a square) forbeing received in a corresponding polygonal opening in a socket wrenchaccessory. In an alternative embodiment, a chuck or another type of toolholder may be affixed to the end of the output member 511. Furtherdetails regarding an exemplar/bit holder are set forth in U.S. patentapplication Ser. No. 12/394,426 which is incorporated herein byreference.

The housing 512 may also receive or be coupled to a rechargeable and/orremovable power source 528 such as a battery pack with one or morebattery cells. Alternative, the power source may be an AC power plugcoupled to the housing. An on-off switch 553 may be coupled to thehousing 512 and may control power-up of the tool as discussed below. Acontrol circuit 530 may be disposed on one or more circuit boards insideof the housing and in electrical communication with the switch 553 andthe power source 528. As shown schematically in FIG. 29, the controlcircuit 530 includes a rotational rate sensor 522 and a microcontroller524 as well as other circuitry for interfacing with the power source528, the on-off switch 553, and the motor 526 and for operating thetool. The control circuit 530 may operate according to one of thecontrol methods discussed above with respect to the other embodiments ofpower tools, or according to one of the alternative control methodsdiscussed below.

The rotational rate sensor 522 may be spatially separated in a radialdirection from the rotational axis of the output member 511 and may beoriented so that it senses rotational movement about the axis 508 of theoutput member 511. A motor drive circuit 525 enables voltage from thepower source 528 to be applied across the motor 526 in either direction.In the exemplary embodiment, the motor drive circuit 525 comprises anH-bridge circuit arrangement although other arrangements arecontemplated. The control circuit 530 of the wrench 510 may also includea temperature sensor 531, a current sensor 532, a tachometer 533 and/ora LED 535. In addition, the controller 524 may be coupled to a directionswitch module 540 that can be actuated by the user to indicate a desireddirection of rotation of the output shaft.

In the exemplary embodiment, the rotational motion sensor 522 isgyroscope, such as a MEMS gyroscope. The operating principle of thegyroscope is based on the Coriolis effect. Briefly, the rotational ratesensor may be comprised of one or more resonating masses. When the powertool is subject to rotational motion about the axis of the outputmember, the resonating mass will be laterally displaced in accordancewith the Coriolis effect, such that the lateral displacement is directlyproportional to the angular rate. It is noteworthy that the resonatingmotion of the mass and the lateral movement of the mass(es) occur in oneor more planes which may be orientated perpendicular to the rotationalaxis 508 of the output shaft 511. Sensing elements in the gyroscopedetect the lateral displacement of the mass(es) and generate anapplicable signal indicative of the lateral displacement. An exemplaryrotational rate sensor is the ADXRS150 or ADXRS300 gyroscope devicecommercially available from Analog Devices, or the ISZ-650 or IXZ-2500gyroscope devices commercially available from InvenSense, Inc. [0001]While the rotational rate sensor 522 described above is presentlypreferred for determining angular displacement of the tool, it isreadily understood that this disclosure is not limited to this type ofsensor. On the contrary, angular displacement may be derived in othermanners and/or from other types of sensors. It is also noted that thesignal from any rotational rate sensor can be filtered in the analogdomain with discrete electrical components and/or digitally withsoftware filters. It is readily understood that accelerometers,compasses, inertial sensors and other types of rotational motion sensorsare contemplated by this disclosure. It is also envisioned that therotational sensor as well as other tool components may be incorporatedinto a battery pack or any other removable pieces that interface withthe tool housing.

During operation, the rotational motion sensor 522 senses and monitorsrotational motion of the housing 512 with respect to the rotational axis508 of the output member 511. A control module implemented by thecontroller 524 receives input from the rotational motion sensor 522 anddrives the motor 526 and thus the output member 511 based upon inputfrom the rotational motion sensor 522. As used herein, the term modulemay refer to, be part of, or include an Application Specific IntegratedCircuit (ASIC); an electronic circuit; a combinational logic circuit; afield programmable gate array (FPGA); a processor (shared, dedicated, orgroup) that executes code; other suitable components that provide thedescribed functionality; or a combination of some or all of the above,such as in a system-on-chip. The term module may include memory (shared,dedicated, or group) that stores code executed by the processor, wherecode, as used above, may include software, firmware, and/or microcode,and may refer to programs, routines, functions, classes, and/or objects.

In power tool 510, the control circuit 530 and its control methodoperate such that user rotation of the housing about the rotational axis508 of the output shaft 511 is used to control motor operation. In anexemplary embodiment, rotational motion of the tool about the rotationalaxis 508 of the output member 511 is monitored using the rotationalmotion sensor 522. The angular velocity, angular displacement, and/ordirection of rotation can be sensed and used as a basis for driving themotor 526 and thus the output shaft 511. With the proposed controlcircuit and method, the control input and the resulting output occur asrotation about the same axis. This results in a highly intuitive controlsimilar to the use of a manual wrench. In an exemplary embodiment, thecontrol scheme is implemented as computer executable instructionsresiding in a memory and executed by a processor of the controller 524.

This type of control scheme requires the tool to know when the operatorwould like to perform work. One possible solution is actuation of theon/off switch 553 that the tool operator actuates to begin work. Forexample, the switch 553 may be include a pushbutton switch accessible onthe exterior of the tool housing. When the operator depresses thepushbutton switch 513 a first time, the tool is powered up (i.e.,battery is connected to the controller and other electronic components).Rotational motion is detected and acted upon only when the tool ispowered up. When the operator depresses the pushbutton switch 513 asecond time, the tool is powered down and thus no longer operational. Inanother example, the on/off switch 513 may be a single pole, singlethrow switch accessible on the exterior of the tool. When the operatorplaces the switch in an ON position, the tool is powered up. When theoperator places the switch in an OFF position, the tool is powered downand no longer operational.

One exemplary power control scheme 540 for the tool 510 is illustratedin FIG. 30A. At step 541, a starting or reference point (θ) isinitialized to zero. Any subsequent angular displacement of the tool isthen measured in relation to this reference. At step 542, angulardisplacement (Δθ) of the tool is monitored. The angular displacement maybe derived from the rate of angular displacement over time or angularvelocity as provided by the rotational rate sensor 522. At step 543, thereference value (θ) is set to be the previous reference value plus thechange in angular displacement (Δθ). At step 544, the controllerdetermines whether the new reference value indicates that the tool hasbeen rotated in the clockwise direction. If so, then at step 545, thecontroller drives the motor to rotate. If not, then at step 546, thecontroller determines whether the new reference value indicates that thetool has been rotated in the counterclockwise direction. If so, then atstep 545, the controller drives the motor to rotate. Whenever the motorrotates, regardless of the direction of rotation of the housing, theoutput shaft 511 will rotate in the direction set by the switch 525.

Subsequent control decisions are based on the absolute angulardisplacement in relation to the starting point as shown at 543. When theangular displacement of the tool remains above the applicable threshold,then the operating speed of the motor is maintained. In this way,continuous operation of the tool is maintained until the tool isreturned to its original position. On the other hand, when the tooloperator rotates the tool in the opposite direction and angulardisplacement of the tool drops below (is less than) a lower threshold,then operation of the motor is terminated at 548. Threshold values mayinclude hysteresis; that is, the lower threshold is set at six degreesfor turning on the motor but set at four degrees for turning off themotor, for example. It is also to be understood that only the relevantsteps of the methodology are discussed above in relation to FIG. 30A,but that other functionality may be needed to control and manage theoverall operation of the wrench.

Another exemplary power control scheme 640 for the tool 510 isillustrated in FIG. 30B. In this control scheme, the power tool isconfigured so that the motor only rotates when the housing 512 isrotated in the same direction as the switch 525 has been set forrotating the output shaft 511. For example, if the switch 525 has beenset to ratchet in the clockwise direction, the motor will only rotate ifthe housing 512 is also rotated in the clockwise direction by about theoutput shaft axis 508. If the housing 512 is rotated in thecounterclockwise direction, then the motor will not rotate. Similarly,if the switch has been set to ratchet in the counterclockwise direction,the motor will only rotate if the housing is also rotated in thecounterclockwise direction about the output shaft axis 508. If thehousing 512 is rotated in the clockwise direction, then the motor willnot rotate.

For this control scheme, it is necessary for the controller to know theposition of the directional control switch 525. FIGS. 31A-31C illustratean exemplary direction switch module 550 that is coupled to thedirection control switch 525 for this purpose. In the exemplaryembodiment, the direction control switch 525 is a knob that can be movedamong three positions: left, center and right. The knob is coupleddirectly to a slide bar 552 having a toothed portion 554. As the knob ismoved from the left position to the right position or vice versa, thetooth of the slid bar engages a wheel 556 of a switching mechanism,rotating the wheel and thereby determining the rotational direction ofthe ratcheting mechanism. When the switch 525 is moved to the leftposition as shown in FIG. 31A, the direction of the ratcheting mechanismis set to counterclockwise. When the switch 525 is moved to the rightposition as shown in FIG. 310, the direction of the ratcheting mechanismis set to clockwise. Further details regarding an exemplary switchingmechanism are set forth in U.S. Pat. Nos. 3,529,498 and 3,621,738 whichare incorporated herein by reference.

When positioned in either the left or right positions, the toothedportion 554 of the slide bar 552 also closes a set of electricalcontacts, thereby communicating the position of the slide bar 552 to thecontroller 524. This will enable the controller to drive the motor onlywhen the tool housing is rotated in the direction set by the position ofthe actuator as will be further described below. For example, when theslide bar 552 is in the left position, as shown in FIG. 31A, the toothedportion 554 electrically connects left electrical contact 556 and centerelectrical contact 558 to indicate to the controller that the userdesires to operate the tool in only the counterclockwise direction. Whenthe slide bar 552 is in the right position, as shown in FIG. 310, thetoothed portion 554 electrically connects a right electrical contact 560and the center electrical contact 558 to indicate to the controller thatthe user desires to operate the tool only in the clockwise direction.When the slide bar 552 is in the center position, as shown in FIG. 31B,the toothed portion 554 does not electrically connect the centerelectrical contact 558 to either the left electrical contact 556 or theright electrical contact 560, which indicates to the controller that theuser does not desire to operate the tool. Other types of switches andsensors for switches could be substituted, as will be apparent to one ofordinary skill in the art.

Referring again to FIG. 30B, at step 641, a starting or reference point(θ) is initialized to zero. Any subsequent angular displacement of thetool is then measured in relation to this reference. At step 642,angular displacement (Δθ) of the tool is monitored. The angulardisplacement may be derived from the rate of angular displacement overtime or angular velocity as provided by the rotational rate sensor 522.At step 643, the reference value (θ) is set to be the previous referencevalue plus the change in angular displacement (Δθ). At step 644, thecontroller determines whether the new reference value indicates that thehousing has been rotated in the clockwise direction about the axis 608.If so, then at step 647, the controller determines whether the switch525 is also set to rotate the output shaft in the clockwise direction.If so, then at step 545, the controller drives the motor to rotate (themotor can be rotated in either direction). If not, then, at step 648,the controller terminates operation of the motor.

If at step 644, the controller determines that the new reference valuedoes not indicate that the housing has been rotated in the clockwisedirection about the axis 508, then at step 646, the controllerdetermines whether the new reference value indicates that the tool hasbeen rotated in the counterclockwise direction. If so, then at step 649,the controller determines whether the switch 525 is also set to rotatethe output shaft in the counterclockwise direction. If so, then at step645, the controller drives the motor to rotate (in either direction).Whenever the motor rotates, regardless of the direction of rotation ofthe housing, the output shaft 511 will rotate in the direction set bythe switch 525.

Subsequent control decisions are based on the absolute angulardisplacement in relation to the starting point as shown at 643. When theangular displacement of the tool remains above the applicable threshold,then the operating speed of the motor is maintained. In this way,continuous operation of the tool is maintained until the tool isreturned to its original position. On the other hand, when the tooloperator rotates the tool in the opposite direction and angulardisplacement of the tool drops below (is less than) a lower threshold,then operation of the motor is terminated at 643. Threshold values mayinclude hysteresis; that is, the lower threshold is set at six degreesfor turning on the motor but set at four degrees for turning off themotor, for example. It is also to be understood that only the relevantsteps of the methodology are discussed above in relation to FIG. 30B,but that other functionality may be needed to control and manage theoverall operation of the wrench.

It should be understood, that in the control schemes described withrespect to FIGS. 30A and 30B, the motor may be driven at a variablespeed having some relationship to the amount or rate of rotation of thehousing 512 about the axis 508, as described above with respect to theother embodiments. In addition, it should be understood, that thecontrol schemes of FIGS. 30A and 30B may incorporate the haptic feedbackalgorithms discussed above to indicate to the user when the tool isactive and ready for use. It should also be understood that the controlschemes of FIGS. 30A and 30B may be used with in-line ratchetingscrewdrivers or other in-line tools where the output axis is coincidentor parallel to the axis of the motor and/or the housing or handle.

FIGS. 32A and 32B illustrate an alternative embodiment of a power socketwrench 510′. The wrench 510′ is similar to the wrench 510 describedabove except that the wrench 510′ is equipped with two drive squares515′, 516′, one extending from each side of a ratchet head 517′. Thedrive squares are configured to receive a socket as is readily known inthe art. In this variant, the motor and the output shaft only need to bedriven in one direction regardless of the direction of rotation of thehousing because one of the drive squares 515′ can be used for clockwiseratcheting rotation, while the other of the drive squares 516′ can beused for counterclockwise ratcheting rotation. Thus, there is no needfor a mechanical switch for switching between clockwise andcounterclockwise rotation. Depending on the desired direction, the userselects the appropriate side of the ratchet head to apply to theworkpiece.

Thus, the wrench 510′ may be programmed to operate according to thecontrol scheme of FIG. 30A, described above. That is, the tool operatoractuates an on/off switch 513′ in order to power up the tool and beginwork. To drive the motor, the user rotates the tool housing about therotational axis of the drive squares. Angular displacement of the toolhousing is monitored in relation to a zero position. The motor is drivenonce the angular displacement exceeds a minimum displacement thresholdand continues until the tool housing is rotated back to the zeroposition. It is understood that the motor is driven in a fixed directionwhich is independent of the direction the tool housing is rotated.

Referring to FIGS. 33-36, in another implementation of the presentdisclosure, one of the motor control schemes described above may beincorporated into a rotary impact driver power tool 760. The impactdriver 760 is comprised generally of a housing 762 having a shape like aconventional power drill. The housing 762 defines a handle portion 763which is gripped by a user during tool operation. An output member 764that includes a tool bit holder extends from one end of the housing andis configured to rotate about its rotational axis 765. In oneembodiment, the rotational axis of the output member 764 may be angledrelative to a longitudinal axis of the handle portion 763 (e.g.,substantially perpendicular). A motor 766 residing in the housing 762 isdrivably connected to the output member 764 to impart rotary motionthereto. An impact mechanism 767 is interposed between the motor 766 andthe output member 764. Further details regarding an exemplary impactmechanism are set forth in U.S. Pat. No. 5,016,501 and U.S. PatentApplication Pub. Nos. 2007/0267207 and 2010/0071923, which areincorporated herein by reference. Other exemplary impact mechanisms canbe found in IDS600 Impact Screwdriver and FDS600 Impact Screwdrivercommercially available from Black & Decker and in the DCF895 ImpactDriver, DCF896 Impact Driver, and the DCF880 Impact Wrench availablecommercially from DeWALT Industrial Tool Co.

Referring to FIGS. 35 and 36, the impact driver 760 includes a printedcircuit board 770 to which is mounted a microcontroller, rotationalmotion sensor (e.g., a gyroscope) and other control electronics, similarto the components of the control circuit of FIG. 7, described above. Theprinted circuit board 770 has a front end portion 776 and a rear endportion 772. The front end portion 776 is sandwiched between a pair ofelastomeric dampers 782 (or springs), one of which is coupled to anexterior wall 778 of the housing 762, and the other of which is coupledto a fixed interior wall 780 of the housing 762. The dampers 782 areoriented to dampen vibrations in a direction Y that is substantiallyperpendicular to the longitudinal axis L of the motor and output shaft.

The rear end portion 772 of the printed circuit board 770 is fixedlyconnected to a floating shoe 774 that is not fixedly connected to thehousing. A depending portion 784 of the shoe 774 is coupled to aplurality of elastomeric dampers 786 (or springs) that abut the interiorwall 780 of the housing and another portion of the housing. The dampers786 are oriented to dampen vibrations in a direction X that issubstantially parallel to the longitudinal axis L. The dampers 782 and786 combine to dampen vibrations from the motor and the impact mechanism(which can generate large vibrations) so that the vibrations do notinterfere with the readings of the rotary motion sensor.

To operate the impact driver, the tool operator actuates an on/offswitch 761 in order to power up the tool and begin work. The userrotates the tool housing 763 about the rotational axis of the outputmember 764 to drive the motor. Angular displacement of the tool housingis monitored in relation to a zero position. In one embodiment, themotor is driven once the angular displacement exceeds a minimumdisplacement threshold and continues until the tool housing is rotatedback to the zero position. When the tool housing is rotated in aclockwise direction, the motor is driven is a clockwise direction. Whenthe tool housing is rotated in a counter-clockwise direction, the motoris driven in a counter-clockwise direction. Thus, the rotationaldirection of the motor is determined by the rotational motion of thetool housing. The impact driver may otherwise operate in a mannersimilar to one or more of the control schemes described above (e.g.,with respect to FIGS. 8A-8C, 9A-9E, 18, 30A, and 30B.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

Example embodiments are provided so that this disclosure will bethorough and will fully convey the scope to those who are skilled in theart. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

What is claimed is:
 1. A power tool comprising: a housing; an outputmember coupled to the housing, the output member including an outputshaft configured to rotate about a longitudinal axis; a switchconfigured to select a desired rotational direction of the output shaftbetween a clockwise direction and a counterclockwise direction; a motorcontained in the housing and drivably connected to the output shaft toimpart rotary motion thereto; a rotational motion sensor arranged in thehousing and operable to detect rotational motion of the housing about arotational axis that is substantially parallel to the longitudinal axisof the output shaft; a controller arranged in the housing to receive afirst signal indicative of the desired rotational direction from theswitch and a second signal indicative of the rotational motion of thehousing from the rotational motion sensor, the controller operable todetermine a direction of the rotational motion of the housing about therotational axis and to drive the motor only when the direction ofrotational motion of the housing is the same as the desired rotationaldirection.
 2. The power tool of claim 1, wherein the controllerdetermines angular displacement of the housing about the rotational axisin relation to a reference position and drives the motor at a rotationalspeed that correlates to the angular displacement of the housing.
 3. Thepower tool of claim 2, wherein the controller resets the referenceposition to zero in response to an input command from an operator of thetool.
 4. The power tool of claim 1, wherein the controller drives themotor at a maximum rotational speed when the angular displacement of thetool exceeds a first threshold and drives the motor at a designatedrotational speed that is less than the maximum rotational speed when theangular displacement of the tool is less than the first threshold butgreater than a second threshold.
 5. The power tool of claim 1, whereinthe output member comprises a ratcheting mechanism configured to rotatethe output shaft in a ratcheting manner in a direction that is the sameas the desired rotational direction.
 6. The power tool of claim 5,wherein the switch is coupled to the ratcheting mechanism to enableswitching the rotation of the output shaft between ratcheting in aclockwise direction and ratcheting in a counterclockwise direction. 7.The power tool of claim 1, wherein the controller drives the motor in aclockwise direction when the desired rotational direction is in aclockwise direction, and rotates the motor in a counterclockwisedirection when the desired rotational direction is in a counterclockwisedirection.
 8. A power tool comprising: a housing; an output membercoupled to the housing, the output member including an output shaftconfigured to rotate about a longitudinal axis; a motor contained in thehousing and drivably connected to the output member to impart rotarymotion thereto; a rotational motion sensor arranged in the housing andoperable to detect rotational motion of the housing about a rotationalaxis that is substantially parallel to the longitudinal axis of theoutput shaft; a controller arranged in the housing to receive a signalindicative of rotational motion from the rotational motion sensor, thecontroller operable to determine a direction of the rotational motion ofthe housing about the rotational axis and to drive the motor so that themotor drives the output shaft in the same direction as the rotationalmotion of the housing.
 9. The power tool of claim 8, wherein thecontroller is operable to drive the motor to cause the output shaft torotate in a clockwise motion about the longitudinal axis when therotational motion of the housing about the rotational axis is clockwise,and to drive the motor to cause the output shaft to rotate in acounterclockwise motion about the longitudinal axis when the rotationalmotion of the housing about the rotational axis is counterclockwise. 10.The power tool of claim 8, wherein the controller is operable todetermine angular displacement of the housing about the rotational axisin relation to a reference position and drives the motor at a rotationalspeed that correlates to the angular displacement of the housing. 11.The power tool of claim 10, wherein the controller resets the referenceposition to zero in response to an input command from an operator of thetool.
 12. The power tool of claim 8, further comprising a switchconfigured to select a desired rotational direction of the output shaftbetween a clockwise direction and a counterclockwise direction.
 13. Thepower tool of claim 12, wherein the controller is operable to drive themotor to cause the output shaft to rotate in a clockwise motion aboutthe longitudinal axis only when the rotational motion of the housingabout the rotational axis is clockwise and the desired rotationaldirection is also clockwise, and to drive the motor to cause the outputshaft to rotate in a counterclockwise motion about the longitudinal axisonly when the rotational motion of the housing about the rotational axisis counterclockwise and the desired rotational motion of the housingabout the rotational axis is also counterclockwise.
 14. The power toolof claim 12, wherein the output member comprises a ratcheting mechanismconfigured to rotate the output shaft in a ratcheting manner in adirection that is the same as the desired rotational direction.
 15. Thepower tool of claim 8, wherein the power tool comprises a rotary impactdriver mechanism configured to impart rotary impacts to the outputshaft.
 16. The power tool of claim 15, wherein the rotational motionsensor is mounted on a board with at least one dampener disposed betweenthe board and the housing to dampen vibrations from the impact drivermechanism.
 17. A power tool comprising: a housing; an output shaftcoupled to the housing and configured to rotate about a longitudinalaxis; a motor contained in the housing and drivably connected to theoutput member to impart rotary motion thereto; a spindle lock disposedbetween the motor and the output shaft, the spindle lock configured toenable torque transmission from the motor to the output shaft when aninput torque is applied by the motor, and configured to prevent torquetransmission from the output shaft to the motor when an input torque isapplied by the output shaft; a rotational motion sensor arranged in thehousing and operable to detect rotational motion of the housing about arotational axis; a current sensor arranged in the housing and operableto detect an amount of current being delivered to the motor; acontroller arranged in the housing to receive a current signal from thecurrent sensor and a rotational motion signal indicative of rotationalmotion of the housing about the rotational axis from the rotationalmotion sensor, wherein the controller is operable to drive the motor ata predetermined power level in correlation to an amount of rotationalmotion of the housing as indicated by the rotational motion signal, andwherein the controller is operable to reduce the power level to apredetermined lower level when the current signal indicates that theamount of current being delivered to the motor exceeds a predeterminedthreshold amount.
 18. The power tool of claim 17 wherein thepredetermined lower level is less than 20% of the predetermined powerlevel.
 19. The power tool of claim 17, wherein the controller isoperable to drive the motor to cause the output shaft to rotate in aclockwise motion about the longitudinal axis when the rotational motionof the housing about the rotational axis is clockwise, and to drive themotor to cause the output shaft to rotate in a counterclockwise motionabout the longitudinal axis when the rotational motion of the housingabout the rotational axis is counterclockwise.
 20. The power tool ofclaim 17, wherein the controller is operable to determine angulardisplacement of the housing about the rotational axis in relation to areference position and drives the motor at a rotational speed thatcorrelates to the angular displacement of the housing.